Myeloproliferative neoplasms (MPNs) are a group of disorders that cause an overproduction of blood cells (platelets, white blood cells and red blood cells) in the bone marrow. MPNs include polycythemia vera (PV), primary or essential thrombocythemia (ET), primary or idiopathic myelofibrosis, chronic myelogenous (myelocytic) leukemia (CML), chronic neutrophilic leukemia (CNL), juvenile myelomonocytic leukemia (JML) and chronic eosinophilic leukemia (CEL)/hyper eosinophilic syndrome (HES). These disorders are grouped together because they share some or all of the following features: involvement of a multipotent hematopoietic progenitor cell, dominance of the transformed clone over the non-transformed hematopoietic progenitor cells, overproduction of one or more hematopoietic lineages in the absence of a definable stimulus, growth factor-independent colony formation in vitro, marrow hypercellularity, megakaryocyte hyperplasia and dysplasia, abnormalities predominantly involving chromosomes 1, 8, 9, 13, and 20, thrombotic and hemorrhagic diatheses, exuberant extramedullary hematopoiesis, and spontaneous transformation to acute leukemia or development of marrow fibrosis but at a low rate, as compared to the rate in CML. The incidence of MPNs varies widely, ranging from approximately 3 per 100,000 individuals older than 60 years annually for CML to 0.13 per 100,000 children from birth to 14 years annually for JML (Vardiman J W et al., Blood 100 (7): 2292-302, 2002).
Accordingly, there remains a need for new treatments of MPNs, as well as other cancers.